1. Field of the Invention
The present invention relates to a positioning apparatus that positions a subject by moving the subject by using a drive element in a first direction, a second direction that is orthogonal to the first direction and a third direction that is orthogonal to the first direction and the second direction and a scanning probe microscope including the same.
2. Description of the Related Art
The scanning probe microscope is a system including a cantilever having a sharpened probe at the free end and a movement mechanism that finely moves the relative positions of the cantilever and a subject (which will be called sample hereinafter) and detects the displacement of the free end of the cantilever due to the interaction between the distal end of the probe and the sample and, at the same time, scans the sample surface with the probe in a plane direction containing a first direction (which will be called X-axis direction hereinafter) and a second direction (which will be called Y-axis direction hereinafter), which is orthogonal thereto, that is, in the plane direction that is horizontal to the sample surface (which will be called XY directions hereinafter) to three-dimensionally measure the information on the surface form or a property of the sample. In measuring the surface form of the sample by means of the scanning probe microscope, the surface form of the sample is measured based on the stroke in the direction that is orthogonal to the XY directions, that is, in the direction that is vertical to the sample surface (which will be called Z-axis direction) by scanning in the XY directions and measuring the space between the sample and the probe from the amount of deformation of the cantilever and moving the probe in the Z-axis direction such that the spacing between the sample and the probe can be kept constant (refer to Web Site of Japanese Patent Office, HOME>Shiryoshitsu (Sonota Sanko Joho)>Hyojungijyutsu-Shu>Hyomenkouzou no Genshi Ryoiki Bunseki (Gijyutsu Naiyo, FIGS. 1 and 2), for example).
The movement mechanism of the scanning probe microscope may often be a positioning apparatus including a piezoelectric element. Since the surface form is tracked and is measured by moving the relative positions of the sample and the probe, the positioning apparatus for use in the scanning probe microscope is only required to scan the sample surface at a predetermined velocity in the XY directions. However, since the fine concaves and convexes on the sample surface must be tracked in the Z-axis direction, a faster responsivity at some slopes on the sample surface may be required than the one for the XY directions.
However, the responsivity of the positioning apparatus that drives in the multiple axial directions depends on the resonance frequency of the entire positioning apparatus including not only the mechanism for movement in the axial direction in which fast driving is desired but also the mechanism in the axial direction for slower driving, which are included in the positioning apparatus. Therefore, in a case of the positioning apparatus with a combination of multiple axes, the fast driving in a specific direction is not allowed.
Thus, in a conventional scanning probe microscope, to improve responsivity of the Z-axis direction, method to separate to a sample side and a cantilever side in binary movement mechanism of XY direction and the Z-axis direction is disclosed by JP-A-10-339735. Also, for similar purpose, a counterbalance method to attach a drive element to cancel the reaction to the movement mechanism for fast driving is disclosed by JP-A-2001-330425. However, the former example may have a problem that the displacement of a sample may occur when the sample is driven in the XY directions or that a large mass sample may not be driven fast in the XY directions since the resonance frequency is reduced inversely with the ½ power of the mass. The latter example may have a problem that two power supplies or a power supply having a double capacity may be required since the double amount of current is required for driving drive elements one of which is added for counter-balance.
It is an object of the invention to provide a positioning apparatus, which drives in multiple axial directions and is suitable for a scanning probe microscope, for preventing the decrease in resonance frequency in the axial direction subject to fast driving due to the crosstalk caused by a combination of a movement mechanism to be driven fast and a movement mechanism to be driven slow and improving the responsivity in the axial direction subject to fast driving by improving the controllable frequency band as a whole such that fast measurement can be allowed, and a scanning probe microscope employing the positioning apparatus.